Re: Physical Layout of disk to use Oracle

From: Adon Keber <adon_at_cool.iskon.local>
Date: 16 Sep 2003 10:10:52 GMT
Message-ID: <slrnbmdodc.1pc.adon@cool.iskon.local>

On Tue, 16 Sep 2003 06:12:17 +1000, Howard J. Rogers wrote:
>>
>> hdisk2 --> Oracle Appplication Software
>> hdisk3 --> SYSTEM Tablespaces(for all instances) + Control File 1
>> hdisk4 --> ROLLBACK Tablespace + Redo Log files + Control File 2
>> hdisk5 --> DATA Tablespace + Control File 3
>> hdisk6 --> INDEX Tablespace + TEMP Tablespace
>> hdisk7 --> ARCHIVE Redo Log destination disk.
>>
>> Can anyone point out if there would be any issues in the above Layout.
>> Please feel free to be as critical as possible....after all I learn
>> from my mistakes only.
>>
>>
>> THANKS!
>
>No real advice this time... except that you're going to get a lot of people
>telling you to "Stripe and Mirror Everything" (SAME), and before you take
>that advice (which is certainly an easy approach), you might care to check
>out www.ixora.com.au, and see what Steve Adams has to say on the subject.

This is the probably the only thing where I don't agree with Steve Adams.

SAME does NOT show lack of DBA skill but it is compromise between conflicting requirements. For example in above layout I see underutilized disks (with assumption that all the hdisk* is the same) with SYSTEM, ARCHIVE and INDEX tablespaces, probable hotspot on ROLLBACK, possibly over utilized DATA.

Designing optimal layout is hard and requires knowledge of applications. The knowledge the DBA mostly don't have in time of instance creation. Also applications are changed or new applications are added to the same instance and load patterns are constantly changed throughout life of the instance.
Also many db instances are both OLTP and DWH in nature so creating optimal physical layout is almost impossible. Should I redesign DB physical layout every time some programmer predicts that his new application would have tables of 500Mb-1Gb in month or two. Or should I add few new disks just for him?

Also Adams himself says: "Indiscriminate broad striping randomizes all I/O and makes service times uniform." And I say - makes service times more uniform and more predictable over the time.

a. Received on Tue Sep 16 2003 - 05:10:52 CDT